Year	US Dollars
1962	630
1963	710
1964	790
1965	890
1966	980
1967	1070
1968	1180
1969	1330
1970	1500
1971	1700
1972	2000
1973	2490
1974	2850
1975	3480
1976	3750
1977	3940
1978	4600
1979	5650
1980	6500
1981	6370
1982	5910
1983	5280
1984	5140
1985	5010
1986	5360
1987	6130
1988	7590
1989	8310
1990	8970
1991	9850
1992	11200
1993	11140
1994	11610
1995	12410
1996	13430
1997	14100
1998	13810
1999	13380
2000	13330
2001	13070
2002	13150
2003	15700
2004	19580
2005	22760
2006	24550
2007	26350
2008	28660
2009	29330
2010	27660
2011	24930
2012	23500
2013	22540
2014	22180
2015	20360
2016	18870
2017	18090